Commit f055affb authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Paul Mackerras
Browse files

[PATCH] powerpc: native atomic_add_unless 



Do atomic_add_unless natively instead of using cmpxchg.
Improved register allocation idea from Joel Schopp.

Signed-off-by: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarPaul Mackerras <paulus@samba.org>
parent 4f629d7d

include/asm-powerpc/atomic.h

+24 −14
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 
typedef struct { volatile int counter; } atomic_t;



#ifdef __KERNEL__

#include <linux/compiler.h>

#include <asm/synch.h>

#include <asm/asm-compat.h>
@@ -176,20 +177,29 @@ static __inline__ int atomic_dec_return(atomic_t *v) 
 * Atomically adds @a to @v, so long as it was not @u.

 * Returns non-zero if @v was not @u, and zero otherwise.

 */

#define atomic_add_unless(v, a, u)			\

({							\

	int c, old;					\

	c = atomic_read(v);				\

	for (;;) {					\

		if (unlikely(c == (u)))			\

			break;				\

		old = atomic_cmpxchg((v), c, c + (a));	\

		if (likely(old == c))			\

			break;				\

		c = old;				\

	}						\

	c != (u);					\

})

static __inline__ int atomic_add_unless(atomic_t *v, int a, int u)

{

	int t;



	__asm__ __volatile__ (

	LWSYNC_ON_SMP

"1:	lwarx	%0,0,%1		# atomic_add_unless\n\

	cmpw	0,%0,%3 \n\

	beq-	2f \n\

	add	%0,%2,%0 \n"

	PPC405_ERR77(0,%2)

"	stwcx.	%0,0,%1 \n\

	bne-	1b \n"

	ISYNC_ON_SMP

"	subf	%0,%2,%0 \n\

2:"

	: "=&r" (t)

	: "r" (&v->counter), "r" (a), "r" (u)

	: "cc", "memory");



	return t != u;

}



#define atomic_inc_not_zero(v) atomic_add_unless((v), 1, 0)



#define atomic_sub_and_test(a, v)	(atomic_sub_return((a), (v)) == 0)